Advanced lithography is a key factor in microelectronic integration. Advanced lithography capability requires a high capital investment for the IC manufacture. The need for accurate machine utilization tracking is driven by increasing pressure to reduce semiconductor wafer cost by maximizing current machine utilization. A generic apparatus and method of accurately tracking the utilization of advanced lithography systems across a diversified mix of technologies is required in order to remain competitive in todays market.
Various methods of semiconductor machine utilization tracking are currently in use throughout the semiconductor industry. Most manufacturers utilize some type of utilization tracking algorithm which calculates a percentage of machine usage per unit of time. These systems require manual data entry through a stand alone computer network system. Data input is typically performed by those individuals responsible for operating or maintaining the equipment. In some instances, the individual is one and the same. This type of machine utilization tracking system is very subjective and does not always provide accurate machine utilization indices.
Another approach has been to record the number of good parts processed through the machine over a defined period of time and calculate machine utilization base on the theoretical best case performance. There are many basic problems with this type of utilization tracking approach. This type of utilization tracking method does not comprehend technology mix being processed through the machine, reworked wafers cycled back to the unit, machine condition during process, or performance change due to piece part degradation. Piece part degradation alone such as UV source can have a significant impact on machine productivity performance. Since UV steppers utilize a light integrator to compensate for fluctuation in lamp intensity by adjusting the shutter time to deliver constant energy to the image plane, the only noticeable effect of intensity loss during aging of the lamp, assuming uniform intensity distribution, is reduced throughput.